ORBID-OA is a single-center, observational study in 30 patients with stable coronary artery disease.

The aim of the study is to analyze the outcomes of main vessel stenting on side branch in calcified bifurcation lesion and identify preprocedural predictors of side branch complication by utilizing two-dimensional (2D) and three-dimensional (3D) frequency domain optical coherence tomography (FD-OCT).

Coronary artery bifurcation lesion is a common lesion subset in PCI accounting for 15-20% of the total number of interventions (1). Treatment of coronary artery bifurcation lesions represents a challenging area in interventional cardiology (2). When compared with non-bifurcation interventions, bifurcation interventions have a lower rate of procedural success, higher procedural costs, longer hospitalization and a higher clinical and angiographic restenosis (3). Factors contributing to this adverse outcome include limitations of angiography in assessment of side-branch (SB) disease severity and the lack of established angiographic predictors of SB patency and lumen compromise. Better understanding of the underlying plaque morphology and plaque composition may facilitate more effective treatment of bifurcation lesions.

Heavy calcification within coronary atherosclerotic plaque adversely influences both clinical and procedural success after percutaneous coronary interventions (PCI) (4,5). The use of drug-eluting stent (DES) in calcified lesions poses special challenges. Atherectomy can facilitate successful stent delivery and expansion in calcified lesions. Orbital atherectomy (OA) is the newly FDA approved device for treatment of severely calcified coronary lesions which works on the principle of elliptical burr movement. The ORBIT I and II clinical trials evaluated the safety of OA in de novo calcified coronary lesions and demonstrated that complication rate was comparable to historical controls of rotational atherectomy (6).

Intravascular imaging has provided new understanding of mechanisms associated with SB compromise following bifurcation PCI (7-9). Plaque shift has been traditionally considered as the principal mechanism for side-branch compromise after main vessel intervention (9), however recent intravascular imaging studies have provided new insights by suggesting carina shift as a major mechanism implicated in side-branch closure (7). Intravascular ultrasound (IVUS) has been used for guidance in bifurcation lesions, aiding the visualization of plaque morphology at the main vessel and the side-branches and helping the selection of stent size and length as well as the selection of stenting strategy. However, due to the low spatial resolution of IVUS, all attempts for three-dimensional visualization have only focused on visualization of the luminal contour and not on the vessel morphology or the vessel-stent interaction. Optical coherence tomography (OCT) has ~10 times higher resolution than IVUS which allows precise evaluation of the microstructure of the vessel wall including lipid pool, fibrous cap, calcification, and thrombus (10). In addition, it provides immediate automated measurements for lumen dimensions before the treatment and precise evaluation of strut apposition and stent expansion after stenting, which is of particular interest in bifurcation PCI, since it's been associated with a higher number of malapposed stent struts and more frequent stent underexpansion leading to higher incidence of stent thrombosis and restenosis.

OCT has been shown to constitute a valuable tool for PCI guidance and also the utility of three-dimensional (3D) renderings for assessing the mechanism of side-branch compromise following intervention in bifurcation lesions. (11,12). The recent development of OCT with online 3D reconstruction allows the operator to obtain a 3D visualization of the lesion and may provide a unique tool for guidance during complex bifurcation PCI and potentially improve stenting results (12). 3D OCT has been used to visualize jailed side branches after implantation of bioresorbable scaffolds in the main branch and develop a new classification system based on the number of SB compartments (13). In addition, its potential clinical application in guiding the rewiring of the distal compartment of the SB ostium (jailed with stent struts after MB stenting) to minimize the risk of floating struts was demonstrated.

The aim of the study is to analyze the outcomes of main vessel stenting on side branch in calcified bifurcation lesion and identify preprocedural predictors of side branch complication by utilizing two-dimensional (2D) and three-dimensional (3D) frequency domain optical coherence tomography (FD-OCT). Thirty consecutive patients with calcified lesions requiring PCI of main vessel with drug eluting stent implantation for the treatment of stable CAD will be included in the study. All potential subjects will sign a separate Mount Sinai surgical/procedure informed consent for their Cardiac Catheterization procedure on the day of their hospital visit.

Patients will undergo coronary angiogram. OCT will be performed to analyze plaque morphology, the extent and location of calcification, side branch size, angle, and ostial involvement. Patients will undergo PCI with stent implantation according to current standards of care. Lesion preparation including lesion pre-dilation, and use of atherectomy and protection devices will be performed at the operator's discretion, followed by MV stenting. The operator will also decide on length and size of the implanted stent. Procedural optimization, such as post-dilation or additional stent implantation will be performed based only on the angiographic findings, according to the discretion of the operator. Coronary angiogram and another OCT pullback will be performed after PCI.

Inclusion Criteria:

• All patients over 18 years of age presenting with stable coronary artery disease.
• Angiographic lesion with severe calcification with or without side branch (SB) in whom provisional main vessel stenting strategy is planned after reviewing angiogram will be recruited

Exclusion Criteria:

• Patients with ostial left main artery lesions or ostial right coronary artery lesions
• Female patients with child bearing potential not taking adequate contraceptives or currently breastfeeding
• Known allergy to acetylsalicylic acid or clopidogrel.
• Planned surgery within 12 months.
• History of bleeding diathesis
• Major surgery within 15 days
• Life expectancy < 12 months.
• Patients with kidney dysfunction (CrCl<30)

Thirty consecutive patients with calcified lesions requiring PCI of main vessel with drug eluting stent implantation for the treatment of stable CAD will be included in the study.